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Nicholas Cox
Nicholas Cox

##VERIFIED## Download File Collection Of Tropical Desert Pla...

For more than four decades, Dr. Michael Balick has studied the relationship between plants and people, working with traditional cultures in tropical, subtropical, and desert environments. He is a specialist in the field known as ethnobotany, working with indigenous cultures to document their plant knowledge, understand the environmental effects of their traditional management systems, and develop sustainable utilization systems-while ensuring that the benefits of such work are always shared with local communities. Dr. Balick has also conducted research in New York City, studying traditional healing practices in ethnic communities of the urban environment. In addition to ethnobotany, particularly of food, medicinal, and toxic plants, Dr. Balick is an expert on the palm family, an economically important family of plants in the tropics.

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B. Jiang, H. Yang, P. Nuntanakorn, M.J. Balick, F. Kronenberg and E.J. Kennelly. 2005. The value of plant collections in ethnopharmacology: a case study of an 85-year-old black cohosh (Actaea racemosa L.) sample. Journal of Ethnopharmacology 96, pp. 521-528. Download as pdf file 295 kb Please view with Internet Explorer

Tropical deserts are located in regions between 15 and 30 degrees latitude. Environment is very extreme. They have the highest average monthly temperature on Earth. Rainfall is sporadic; precipitation may not be observed at all in a few years. In addition to these extreme environmental and climate conditions, most tropical deserts are covered with sand and rocks, and thus too flat and lacking in vegetation to block out the wind. Wind may erode and transport sand, rocks and other materials; these are known as eolian processes. Landforms caused by wind erosion vary greatly in characteristics and size. Representative landforms include depressions and pans, Yardangs, inverted topography and ventifacts. No significant populations can survive in tropical deserts due to extreme aridity, heat and the paucity of vegetation; only specific flora and fauna with special behavioral and physical mechanisms are supported. Although tropical deserts are considered to be harsh and barren, they are in fact important sources of natural resources and play a significant role in economic development. Besides the equatorial rainforest, there are many hot deserts situated in the tropical zone.

Another significant determinant of tropical desert climate is the presence of subtropical high pressure throughout the year; this involves dry and hot descending air cells named Hadley cells. Specifically, Hadley cells dry out the air and inhibit condensation. Additionally, as the distance from the moisture source increases, the aridity increases.[citation needed]

There are some other reasons for significant changes in temperature in tropical deserts. For instance, a lack of water and vegetation on the ground can enhance the absorption of the heat due to insolation. Subsiding air from dominant high pressure areas in a cloud-free sky can also lead to large amounts of insolation; a cloudless sky enables day temperature to escape rapidly at night.[2]

Wind greatly contributes to aridity in tropical deserts. If wind speed exceeds 80 km/h, it can generate dust storms and sandstorms and erode the rocky surface.[3] Therefore, wind plays an important role in shaping various landforms. This phenomenon is known as the eolian process. There are two types of eolian process: deflation and abrasion.

For fauna, the easiest way is to stay away from the surface of the tropical deserts as much as possible to avoid the heat and aridity. As a result of the scarcity of water, most animals in these regions get their water from eating succulent plants and seeds, or from the tissues and blood of their prey.[7] They also have specific ways to store water and prevent water from leaving their bodies. Some animals live in burrows under the ground which are not too hot and relatively humid; they stay in their burrows during the heat of the day, and only come out to seek food at night. Examples of these animals include kangaroo rats and lizards.[7] Other animals, such as wolf spiders and scorpions, have a thick outer covering that minimizes moisture loss. Animals in tropical deserts have also been found to concentrate their urine in their kidneys to excrete less water.[7]

Representative fauna in tropical deserts include the armadillo lizard, banded Gila monster, bobcat, cactus wren and cactus ferruginous pygmy owl. Moreover, some other animals in deserts including coyote, desert bighorn sheep, desert kangaroo rat, desert tortoise, javelina and Mojave rattlesnake, cougar. Overall, different tropical deserts have different species, for example, Sonoran Desert toad, Sonoran pronghorn antelope are typical animals in Sonoran Desert.[9]

Rich and sometimes unique mineral resources are located in tropical deserts. Representative minerals include borax, sodium nitrate, sodium, iodine, calcium, bromine, and strontium compounds. These minerals are created when the water in desert lakes evaporates.[10]

Tropical deserts have various semi-precious and precious gemstones. The Some common semi-precious gemstones including chalcedony, opal, quartz, turquoise, jade, amethyst, petrified wood, and topaz. Precious gemstones such as diamonds are used in jewellery and decoration. Although some gemstones can also be found in temperate zones throughout the world, turquoise can only be found in tropical deserts. Turquoise is a very valuable and popular opaque gemstone, with a beautiful blue-green or sky-blue colour and exquisite veins.[10]

The desert rose (Adenium obesum) is a striking plant with succulent stems and deep red flowers. Native to the Sahel regions, south of the Sahara (from Mauritania and Senegal to Sudan), and tropical and subtropical eastern and southern Africa and Arabia. The Desert Rose is also known as Desert Azalea, Mock Azalea, Sabi Star, Impala Lily, and Kudu Lily.

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In order to provide species diversity values for African tropical forests, we used the map of Mayaux et al. [50] depicting land cover types across Africa and Madagascar for the year 2000. The map consists of 27 different land cover layers. We selected six of them that consisted mostly, or originally, of tropical forests, namely evergreen forests, degraded evergreen forests, submontane forests, montane forests, swamp forests and mosaic forest-croplands. The original resolution of the map is 1 km2. We aggregated the selected land cover at a resolution of 0.1 (ca. 11 km2) because our georeferenced records are generally not that precise. The resulting forest area layer was then arbitrarily divided into a West African block (west to the Dahomey Gap), a central African block (east of the Dahomey Gap, west of the East African rift), and an eastern African block (east of the East African rift) (Additional file 3). Using these subunits we estimated the number of records, species richness, and number of sub-endemics (considered as a species with 90% or more of its records located within the forest layer) in total and for five different growth forms defined above for African forests in general and for each forest bloc (west, central and east).

Collecting dates ranged from 1782 to 2015. Collecting intensity across tropical Africa through time has generally increased, though with lower collecting efforts in the early 1980s, to 2005, after which there has been a significant decline to the present (Fig. 4a). Collecting intensity per country shows different histories, with different periods of intense and low collecting efforts (Additional file 6). For example, DRC knew its highest period of botanical collections from the 1930s to the 1960s (Additional file 6). In contrast, Benin has experienced intense collecting over the last 20 years (Additional file 6). Other countries, such as Cameroon, have known a sustained and important collecting intensity since the 1960s up until 2010.

Time lapse of botanical collecting history across tropical Africa. The map represents the date of the first botanical collection made within each 0.5 sampling unit. Dashed lines represent the limits for tropical Africa as defined in our study. Map based on georeferenced herbarium records, silica gel samples and plot data. An animated gif version of this map is available at:

When limited to tropical African forests (Additional file 3), RAINBIO records relate to a total of 15,387 vascular plant species, of which 3013 are scored as trees, 5755 as herbs, 1637 as lianas and 3158 as shrubs (Table 3). As expected, the central African forests represent the most species rich block with 10,306 species, followed by the east African forests with 6789 species and West Africa with 4396 species. The endemism rate for Central African forests is 29.1% (2997 out of 10,306 species endemic), 7.4% for east African forests (504 out of 6789 species) and 11.4% West African forests (503 out of 4396 species). The top 20 most species-rich families found in tropical African forests are provided in Table 4.

No country in tropical Africa can be regarded as botanically well explored. Larger areas with no or limited data are still plentiful. Given the observed declining trends in collecting efforts (Fig. 4a) [25], we appeal not only for additional collecting efforts, but also for increased digitization of tropical African plant collections. This will depend on the availability of major funding, mostly at governmental level. In tropical Africa, the major gaps in availability of digital specimen data are in Nigeria, the Central African Republic, South Soudan, the Republic of the Congo and Angola. We believe these to be true gaps, and therefore regions for which comparatively low numbers of specimens have been collected to date. The gap in the availability of data from the DRC should at least partly be overcome soon due to major digitization efforts at BR [56]. Here, we highlight several regions (namely PSUs) we believe would provide a significant amount of new data to our understanding of the tropical African flora in the same spirit as other studies [24, 25]. 041b061a72


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